/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *  http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mlizhi.base.codec.binary;

import com.mlizhi.base.codec.BinaryDecoder;
import com.mlizhi.base.codec.BinaryEncoder;
import com.mlizhi.base.codec.DecoderException;
import com.mlizhi.base.codec.EncoderException;


/**
 * Translates between byte arrays and strings of "0"s and "1"s.
 * 
 * TODO: may want to add more bit vector functions like and/or/xor/nand 
 * TODO: also might be good to generate boolean[] from byte[] et. cetera.
 * 
 * @author Apache Software Foundation
 * @since 1.3
 * @version $Id: BinaryCodec.java 798433 2009-07-28 07:53:10Z ggregory $
 */
public class BinaryCodec implements BinaryDecoder, BinaryEncoder {
/*
 * tried to avoid using ArrayUtils to minimize dependencies while using these empty arrays - dep is just not worth
 * it.
 */
/** Empty char array. */
private static final char[] EMPTY_CHAR_ARRAY = new char[0];

/** Empty byte array. */
private static final byte[] EMPTY_BYTE_ARRAY = new byte[0];

/** Mask for bit 0 of a byte. */
private static final int BIT_0 = 1;

/** Mask for bit 1 of a byte. */
private static final int BIT_1 = 0x02;

/** Mask for bit 2 of a byte. */
private static final int BIT_2 = 0x04;

/** Mask for bit 3 of a byte. */
private static final int BIT_3 = 0x08;

/** Mask for bit 4 of a byte. */
private static final int BIT_4 = 0x10;

/** Mask for bit 5 of a byte. */
private static final int BIT_5 = 0x20;

/** Mask for bit 6 of a byte. */
private static final int BIT_6 = 0x40;

/** Mask for bit 7 of a byte. */
private static final int BIT_7 = 0x80;

private static final int[] BITS = {BIT_0, BIT_1, BIT_2, BIT_3, BIT_4, BIT_5, BIT_6, BIT_7};

/**
 * Converts an array of raw binary data into an array of ASCII 0 and 1 characters.
 * 
 * @param raw
 *  the raw binary data to convert
 * @return 0 and 1 ASCII character bytes one for each bit of the argument
 * @see com.mlizhi.base.codec.BinaryEncoder#encode(byte[])
 */
public byte[] encode(byte[] raw) {
return toAsciiBytes(raw);
}

/**
 * Converts an array of raw binary data into an array of ASCII 0 and 1 chars.
 * 
 * @param raw
 *  the raw binary data to convert
 * @return 0 and 1 ASCII character chars one for each bit of the argument
 * @throws EncoderException
 *  if the argument is not a byte[]
 * @see com.mlizhi.base.codec.Encoder#encode(Object)
 */
public Object encode(Object raw) throws EncoderException {
if (!(raw instanceof byte[])) {
throw new EncoderException("argument not a byte array");
}
return toAsciiChars((byte[]) raw);
}

/**
 * Decodes a byte array where each byte represents an ASCII '0' or '1'.
 * 
 * @param ascii
 *  each byte represents an ASCII '0' or '1'
 * @return the raw encoded binary where each bit corresponds to a byte in the byte array argument
 * @throws DecoderException
 *  if argument is not a byte[], char[] or String
 * @see com.mlizhi.base.codec.Decoder#decode(Object)
 */
public Object decode(Object ascii) throws DecoderException {
if (ascii == null) {
return EMPTY_BYTE_ARRAY;
}
if (ascii instanceof byte[]) {
return fromAscii((byte[]) ascii);
}
if (ascii instanceof char[]) {
return fromAscii((char[]) ascii);
}
if (ascii instanceof String) {
return fromAscii(((String) ascii).toCharArray());
}
throw new DecoderException("argument not a byte array");
}

/**
 * Decodes a byte array where each byte represents an ASCII '0' or '1'.
 * 
 * @param ascii
 *  each byte represents an ASCII '0' or '1'
 * @return the raw encoded binary where each bit corresponds to a byte in the byte array argument
 * @see com.mlizhi.base.codec.Decoder#decode(Object)
 */
public byte[] decode(byte[] ascii) {
return fromAscii(ascii);
}

/**
 * Decodes a String where each char of the String represents an ASCII '0' or '1'.
 * 
 * @param ascii
 *  String of '0' and '1' characters
 * @return the raw encoded binary where each bit corresponds to a byte in the byte array argument
 * @see com.mlizhi.base.codec.Decoder#decode(Object)
 */
public byte[] toByteArray(String ascii) {
if (ascii == null) {
return EMPTY_BYTE_ARRAY;
}
return fromAscii(ascii.toCharArray());
}

// ------------------------------------------------------------------------
//
// static codec operations
//
// ------------------------------------------------------------------------
/**
 * Decodes a char array where each char represents an ASCII '0' or '1'.
 * 
 * @param ascii
 *  each char represents an ASCII '0' or '1'
 * @return the raw encoded binary where each bit corresponds to a char in the char array argument
 */
public static byte[] fromAscii(char[] ascii) {
if (ascii == null || ascii.length == 0) {
return EMPTY_BYTE_ARRAY;
}
// get length/8 times bytes with 3 bit shifts to the right of the length
byte[] l_raw = new byte[ascii.length >> 3];
/*
 * We decr index jj by 8 as we go along to not recompute indices using multiplication every time inside the
 * loop.
 */
for (int ii = 0, jj = ascii.length - 1; ii < l_raw.length; ii++, jj -= 8) {
for (int bits = 0; bits < BITS.length; ++bits) {
if (ascii[jj - bits] == '1') {
l_raw[ii] |= BITS[bits];
}
}
}
return l_raw;
}

/**
 * Decodes a byte array where each byte represents an ASCII '0' or '1'.
 * 
 * @param ascii
 *  each byte represents an ASCII '0' or '1'
 * @return the raw encoded binary where each bit corresponds to a byte in the byte array argument
 */
public static byte[] fromAscii(byte[] ascii) {
if (isEmpty(ascii)) {
return EMPTY_BYTE_ARRAY;
}
// get length/8 times bytes with 3 bit shifts to the right of the length
byte[] l_raw = new byte[ascii.length >> 3];
/*
 * We decr index jj by 8 as we go along to not recompute indices using multiplication every time inside the
 * loop.
 */
for (int ii = 0, jj = ascii.length - 1; ii < l_raw.length; ii++, jj -= 8) {
for (int bits = 0; bits < BITS.length; ++bits) {
if (ascii[jj - bits] == '1') {
l_raw[ii] |= BITS[bits];
}
}
}
return l_raw;
}

/**
 * Returns <code>true</code> if the given array is <code>null</code> or empty (size 0.)
 * 
 * @param array
 *the source array
 * @return <code>true</code> if the given array is <code>null</code> or empty (size 0.)
 */
private static boolean isEmpty(byte[] array) {
return array == null || array.length == 0;
}

/**
 * Converts an array of raw binary data into an array of ASCII 0 and 1 character bytes - each byte is a truncated
 * char.
 * 
 * @param raw
 *  the raw binary data to convert
 * @return an array of 0 and 1 character bytes for each bit of the argument
 * @see com.mlizhi.base.codec.BinaryEncoder#encode(byte[])
 */
public static byte[] toAsciiBytes(byte[] raw) {
if (isEmpty(raw)) {
return EMPTY_BYTE_ARRAY;
}
// get 8 times the bytes with 3 bit shifts to the left of the length
byte[] l_ascii = new byte[raw.length << 3];
/*
 * We decr index jj by 8 as we go along to not recompute indices using multiplication every time inside the
 * loop.
 */
for (int ii = 0, jj = l_ascii.length - 1; ii < raw.length; ii++, jj -= 8) {
for (int bits = 0; bits < BITS.length; ++bits) {
if ((raw[ii] & BITS[bits]) == 0) {
l_ascii[jj - bits] = '0';
} else {
l_ascii[jj - bits] = '1';
}
}
}
return l_ascii;
}

/**
 * Converts an array of raw binary data into an array of ASCII 0 and 1 characters.
 * 
 * @param raw
 *  the raw binary data to convert
 * @return an array of 0 and 1 characters for each bit of the argument
 * @see com.mlizhi.base.codec.BinaryEncoder#encode(byte[])
 */
public static char[] toAsciiChars(byte[] raw) {
if (isEmpty(raw)) {
return EMPTY_CHAR_ARRAY;
}
// get 8 times the bytes with 3 bit shifts to the left of the length
char[] l_ascii = new char[raw.length << 3];
/*
 * We decr index jj by 8 as we go along to not recompute indices using multiplication every time inside the
 * loop.
 */
for (int ii = 0, jj = l_ascii.length - 1; ii < raw.length; ii++, jj -= 8) {
for (int bits = 0; bits < BITS.length; ++bits) {
if ((raw[ii] & BITS[bits]) == 0) {
l_ascii[jj - bits] = '0';
} else {
l_ascii[jj - bits] = '1';
}
}
}
return l_ascii;
}

/**
 * Converts an array of raw binary data into a String of ASCII 0 and 1 characters.
 * 
 * @param raw
 *  the raw binary data to convert
 * @return a String of 0 and 1 characters representing the binary data
 * @see com.mlizhi.base.codec.BinaryEncoder#encode(byte[])
 */
public static String toAsciiString(byte[] raw) {
return new String(toAsciiChars(raw));
}
}
